Referring now to FIG. 10 and FIG. 11, a seat track apparatus in the related art will be described. FIG. 10 is a front view of a seat track in the related art, and FIG. 11 is a plan view of FIG. 10.
In these drawings, an upper rail 1 disposed on the seat side engages a lower rail 3 disposed on the floor side so as to be movable in the direction indicated by an arrow A.
Reference numeral 5 designates a lock mechanism which prohibits the movement of the upper rail 1. The lock mechanism 5 includes lock grooves 3a formed on the lower rail 3 and a lock member 7 disposed on the upper rail 1.
The lock grooves 3a of the lower rail 3 include a plurality of lock grooves formed along the direction of movement of the upper rail 1 (the direction indicated by the arrow A), and the depth direction thereof intersects the direction of movement of the upper rail 1 (the direction indicated by the arrow A).
The lock member 7 disposed on the upper rail 1 is formed by bending a wire rod having resiliency, is disposed on a side surface of the upper rail 1, and includes lock portions 7a at four positions so as to be engageable and disengageable with the lock grooves 3a of the lower rail 3. The lock member 7 is arranged along the direction of movement of the upper rail 1 and, in a natural state, is locked at both end portions thereof with the upper rail 1 so that the lock portions 7a engage the lock grooves 3a. The lock member 7 is formed with loop portions 7b for increasing an urging force in the direction to lock the lock portions 7a to be locked in the lock grooves 3a. 
An operation of the configuration described above will be described. In the state shown in FIG. 10 and FIG. 11, the lock portions 7a of the lock member 7 disposed on the upper rail 1 engage the lock grooves 3a of the lower rail 3, so that the movement of the upper rail 1 is prohibited, and the lock mechanism 5 is brought into a locked state.
Here, when an intermediate portion of the lock member 7 is pushed downward in the direction indicated by an arrow B in FIG. 10, the lock portions 7a are disengaged from the lock grooves 3a of the lower rail 3, so that the movement of the upper rail 1 is enabled and the lock mechanism 5 is brought into an unlocked state (for example, see Patent Document 1).
Patent Document 1: JP-A-7-195964 (FIG. 21, FIG. 22)